Automatic protection apparatus for span lines employed in high speed digital systems

In a telecommunications system including a plurality of service span lines connected in series relationship between a near end office and a far end office to afford communication between said offices via a digital data signal transmitted on said lines, with said signal comprising a given number of data bits per frame, with at least one parity bit indicative of the count of said data bits as being even or odd, comprising:

• a protection switch control unit at each end of said span line and a line service terminal at each end of said span line coupled to said associated protection switch control unit, said service terminal including parity insertion means for modifying said parity bit on a frame to frame basis;
• means responsive to a failure of said service line and coupled to said line service terminal to modify said parity bit for transmission of a code over said service line indicative of a line failure;
• and
• logic means coupled to said protection switch control unit to transfer said failed line at both said near and far end following the occurrence of said failure.

An automatic protection apparatus for a telephone system of the type including at least one service line terminal associated with a service line and at least one protection line terminal associated with a protection line, with said service and protection lines extending between a near and a far central office for transmitting digital data therebetween, with said data as transmitted comprising a number of sucesssive data frames, wherein each frame has a predetermined number of data bits and at least one parity bit indicative of the count of said data bits in said frame being odd or even, comprising:

• a first alarm interface unit coupled to said service line terminal and operative to monitor said service line to detect a failure;
• a second alarm interface unit coupled to said protection line terminal and operative to monitor said protection line to detect a failure;
• a service line control bus coupled to said first alarm interface unit for providing a plurality of data output lines;
• a protection line control bus coupled to said second alarm interface unit to provide a plurality of data output lines;
• protection switch control means coupled to one of said data output lines from each of said service and protection line buses to allow said first and second alarm interface units to communicate with said protection switch control means, said protection switch control means modifying said parity bits for communicating with said far end terminal connected to said service line;
• first data transfer input means associated with said service line and having an input coupled to another output data line from said service line bus and an input coupled to a transmit side of said service line;
• first data transfer output means associated with said service line and having one input coupled to said service line bus and an output coupled to said receive side of said service line;
• second data transfer input means associated with said protection line and having one input coupled to said protection line bus and an output coupled to said first data output associated with said service line, and an input coupled to said receive side of said protection line,
• second data transfer output means associated with said protection line and having one input coupled to said protection line bus and an output coupled to the transmit side of said protection line;
• a data bus coupled between said first data transfer input means and said second data transfer output means;
• whereby upon detection of a failure by said first alarm interface unit said protection switch control operates to connect the transmit side of said service line to the transmit side of said protection line via said first data transfer input means and said second data transfer output means and to connect said receive side of said service line to said receive side of said protection line via said second data transfer input means and said first data transfer output means.